GA wires up to SharePoint 2010 tightly. Thanks to the way SharePoint 2010 uses master pages, it’s a breeze to hook it up (almost). I’m using GA for multiple sites, some are SharePoint 2010 WCM sites and some are not. As you know, SharePoint already has some built in usage analysis capabilities and they are pretty good, 2010 is way better than 2007. GA extends these capabilities and provides a more common interface and set of tools for slicing your web site usage data.
GA is not the most robust analytics package out there, but it’s a great place to start if you’re not already using a web analytics package. It will show you all the main things you need to know, and in time as you’re usage becomes more sophisticated, you will at least know what you need in your next package (the one that is NOT free)!